This invention relates to input screens and combined input/display screens for inputting and/or displaying graphic information in connection with a data storage and/or data processing system.
Touch-pad display screens have found wide application in Personal Digital Assistants (PDAs), ultra-compact personal computers, with built-in operating systems, that are optimized for scheduling and other high-mobility operations. During the past several years, the popularity of PDAs has soared. Corporations such as Sharp, Casio, Philips, 3-Comm, and Hewlett-Packard have entered the fray. Most have flash memory, a small liquid-crystal-display touch-pad screen, a user input device which may be either a barely-usable, miniature keyboard, and/or a touch pad incorporated into the screen, as well as a communications port for transferring files between the PDA and a less-portable computer. A high-end PDA may incorporate a modem and communications software, as well as drawing, word-processing and spreadsheet software. A writing stylus, or xe2x80x9cpenxe2x80x9d, may be supplied, with which the user may write and draw on the touch-pad screen. The PDA may also be equipped with a menu system which requires low-resolution inputs, thereby allowing the user to simply touch the screen at selected touch key locations with his finger to select menu options. The touch-pad feature has great utility on a PDA, as nearly all PDAs are too small to incorporate a keyboard large enough for efficient touch typing. Thus, handwriting and drawings are initially stored as bit-mapped patterns. With writing recognition software that is supplied with many of the PDAs, a user""s handwriting can be converted to ASCII text. Compared with desk-top and lap-top computer systems, PDAs generally have very limited memory storage capabilities. However, the average amount of memory being supplied with PDAs is growing rapidly. Already, PDAs with 16 megabytes of flash memory are available. As it becomes possible to load an entire novel or textbook into the memory of a PDA, it is likely that they will find wide use as electronic editing and annotation devices.
Lap-top computers are equipped, almost exclusively, with LCD displays. Within the past year, flat screen displays utilizing LCD technology have become sufficiently inexpensive that they are beginning to replace cathoderay-tube (CRT) displays used with desk-top systems. Because touch-pad functionality can be readily incorporated in an LCD display, it is likely that large numbers of both lap-top and desk-top systems will soon incorporate LCD display screens with touch-pad functionality. The incorporation of touch pad functionality promises to facilitate rapid user interaction with the computer system. For example, the computer system may be programmed to initiate a particular task when a certain letter is drawn with a finger tip or stylus on the touch pad. An additional example is the programming of the computer system so that the edges of the touch pad mimic on-screen scrollbars. A touch pad will also permit the user to enter data in handwriting and to sign documents with a bit-mapped copy of his signature. With the availability of touch-pad systems, electronic editing and annotating of documents will become much more widespread. There is little doubt that the incorporation of touch-pad functionality will greatly enhance the flexibility of personal computer systems. The incorporation of the touch pad feature in a desktop system is expected to reduce the frequency of repetitive motion injuries, as little arm or wrist motion is required.
Many different types of devices presently exist which utilize tactile sensing to provide inputs to a data processing system. These devices sense the position of a finger or stylus at successive intervals on a touch sensitive surface. The touch detection mechanism typically relies on localized changes in either conductivity or capacitance from a reference value caused by the presence of the finger or stylus on or near the touch sensitive surface. A touch screen display typically has both horizontal and vertical scanning circuitry. The location and direction of a touch input is determined during the periodic scanning of both horizontal and vertical screen elements. For example, if a screen has 600 elements arrayed vertically along the screen""s horizontal axis and 400 elements arrayed horizontally along the screen""s vertical axis, a capacitive change from a standard value at the intersection of any horizontal element and a vertical element will indicate a touch input at the intersection location.
In U.S. Pat. No. 4,013,835 to Eachus, et al., a touch pad is formed from a layer of a variable-resistance material, such as a silicone rubber membrane embedded with silver particles, which overlies a first set of parallel conductor strips which, in turn, overlie a second set of parallel conductor strips. Each conductor strip of the first set incorporates a plurality of serially-connected, open rectangles. Each rectangle surrounds a center conductive island which is in permanent contact with a conductor strip of the second set. When the membrane is compressed in the area of an open rectangle by pressure exerted by a finger or stylus, the membrane becomes conductive in the compressed region, and electrical contact is made between the rectangle and the surrounded island. Position can be determined by sequentially scanning the both sets of conductor strips at the periphery of the touch pad and determining current flow from a conductor of the first set to a conductor of the second set. Up to a maximum value, current flow will increase with pressure.
In U.S. Pat. No. 4,698,461 to Meadows, et al., a touch panel incorporates an upper layer of uniform resistivity. Panel scanning signals are applied to excite selected touch surface edges so as to establish an alternating current gradient across the panel surface. When the surface is touched, a current flows from each excited edge through the resistive surface and is either capacitively or conductively coupled to earth ground potential through the user""s finger and body. As resistance increases with the distance from the edges of the panel, the touch location can be determined by measuring the current flows during the scanning process.
Cirque Corporation, a company noted for its touch-pad sensing devices, has received several patents covering the technology which descend from U.S. application Ser. No. 7/914,043 filed by Gerpheide, et al. On Jul. 13, 1992. One of the latest of these is U.S. Pat. No. 5,861,875. A touch-sensitive pad includes a plurality of capacitive elements formed by two perpendicularly-overlapping, dielectrically-insulated arrays of parallel electrode strips. The capacitive coupling of an object, such as a finger or stylus, to the capacitive elements is sensed to determine the object""s horizontal and vertical (x and y) position with respect to the touch surface of the pad. This device is of interest because capacitive balance measurement circuitry and capacitive balance ratio determination circuitry have been included which increase position detection resolution beyond an object""s coarse position, which is a function of the separation of the parallel electrode strips within the two arrays. In addition, the circuitry provides for a determination of the vertical proximity of an object to the touch pad so that a determination can be made as to whether or not a determination of the x and y position is meaningful.
In U.S. Pat. No. 5,194,862 to Edwards, a sensor array system includes a row and column array of individual sensing elements, each of which has a bistable circuit which adopts one or the other of two stable states depending on whether or not a touch input (made by either a stylus or finger) exists at the sensing element location. The rows of sensing elements are periodically reset in sequence by a scanning address circuit and the states of their bistable circuits are determined at regular intervals related to resetting by a detection circuit using active matrix addressing of the sensing elements. The array of sensing elements is fabricated using thin film transistor technology. The system can be used as an overlay to a display device such as a matrix liquid crystal display screen.
U.S. Pat. No. 5,122,787 to Fujita, et al., discloses a ferroelectric liquid crystal touch panel that includes two mutually perpendicular sets of parallel electrodes arrayed in spaced-apart parallel planes. A ferroelectric liquid crystal positioned between the electrodes at the intersection of each electrode pair. The location of touch inputs on the panel are determined by scanning peripheral circuitry which detects electromotive forces which are generated when a ferroelectric crystal is compressed by a touch input.
A different approach is taken by U.S. Pat. No 5,777,596 to Herbert. Touch inputs made with a finger or stylus on a liquid crystal display are detected by scanning circuitry, which continuously compares charge times of the constituent liquid crystal elements to a reference value. The results of the comparison determine which elements in the display are being touched.
The combination display and sensing device of U.S. Pat. No. 5,847,690 to Boie, et al., incorporates modified liquid crystal display elements a black matrix layer adapted for sensing screen touch locations. A scanned electrical signal applied to the display elements produces an output signal indicative of a touched location on the screen.
Touch-sensitive display screens almost invariably require conductive circuit elements to be embedded within the display panel itself. Either these elements must be so delicate that they do not substantially interfere with the transmission or reflection of light, or they must be transparent. Indium tin oxide is one of the few known transparent solid materials. As such, it has found widespread use in the manufacture of liquid crystal displays having touch-sensitive input capability.
Display screens incorporating touch pad functionality are manufactured for a wide variety of applications. Manufacturers design the properties of the touch screen to meet certain needs of the consumer. Two properties which may vary from one screen to another are resolution and touch sensitivity.
Resolution may be defined as the ability of the screen to resolve two nearby points on the screen. It can also be defined as the smallest area on the screen surface recognizable as a single point or pixel. Low-resolution screens would be adequate, or even desirable, for certain applications such as region selection, check boxes, or highlighting portions of displayed documents. High-resolution screens would be desirable for sketching, handwriting input, digital signatures, and any other task where precise, smoothly drawn lines are required. A drawback of a high resolution screen is that greater processing power is required to manage the resulting greater data input.
Touch sensitivity, on the other hand, refers to the amount of pressure applied to the screen surface that is required to activate a pixel. A high level of touch sensitivity (i.e., pixels are activated with low applied pressure) is useful when a high level of dexterity is required for a given task. Sketching or handwriting, for example, are best registered on a screen having high touch sensitivity. Screens possessing low touch sensitivity (i.e., pixels are activated with high applied pressure) are less likely to register a touch from either inadvertent touching or from resting the palms of the hands on the screen.
What is needed is a touch screen having varying combinations of resolution and touch sensitivity for different applications. Different combinations of these two properties will enhance the functionality of the user interface and will optimize inputs for a particular task.
This invention includes a touch screen panel having varied combinations of resolution and touch sensitivity. The touch screen panel may also incorporate display functionality. For a first embodiment of the invention, the majority of the screen area exhibits low resolution, high touch force characteristics. This large area might be used for highlighting and simple annotation, thereby minimizing processor bandwidth and providing rejection of inadvertent touchings. A smaller area of the screen exhibits low touch force and high resolution properties. This smaller area may be used for digital signature input or for security marking input. The smaller area may be placed in a corner of the screen where it is unlikely to be inadvertently touched. For a second embodiment of the invention, the peripheral regions (i.e., regions near the circumferential edge) of the screen are provided with regions of high-resolution, low-touch-force properties. These regions may be programmed to act as scroll bars, which would allow the user to change locations in a document when only a portion of the document is displayed on the screen. In the central regions of the screen, lower-resolution, higher-touch-force properties provide palm rejection and coarse marking or movement capability with low bandwidth utilization.
Either the varied screen properties may be incorporated into the screen during its manufacture, or the screen may be designed so that the varied properties are programmable by the user. In order to provide regions on the display screen of different resolution during the manufacturing process, several approaches are possible. One approach requires the fabrication of a smaller screen within the larger screen, with both the smaller and larger screens having their own dedicated sensing and scanning circuitry. Different properties are incorporated into the circuitry of each screen. Another approach utilizes the same scanning circuitry for both high and low-resolution regions of the screen. The screen is manufactured in such as manner so as to either accommodate high-resolution touch sensing over the entire area of the screen or only in certain preset regions. If the entire screen can accommodate high-resolution touch sensing, then the system is programmed to use low-resolution scanning as the default operational condition. When scanning in the high-resolution mode, every sensing element is scanned. However, when operating in the low-resolution scanning mode, only a fraction of the sensing elements are scanned. When a touch input is sensed in the designated high-resolution regions, the system immediately switches to high-resolution scanning. High-resolution scanning is maintained until the system senses a touch input in a low-resolution region of the screen, at which time the system reverts to low-resolution scanning. It should be readily apparent that multiple scanning modes can be hard-wired into the screen""s scanning circuitry at the time of manufacture or the screen can be manufactured so that the scanning modes are programmable. Still another approach to providing for low and high-resolution detection is through the use of a balance detection system, such as that employed in the referenced patent to Gerpheide, et al. Balance detection circuitry can be activated when a touch input is sensed in the a designated high-resolution region, and deactivated when a touch input is sensed in a designated low-resolution region.
Although programmable region-specific resolution may be readily implemented for most types of touch screen panels, only certain types of touch-sensitive panels may readily incorporate programmability for touch sensitivity. As a general rule, touch sensitivity programmability may be implemented for only those displays for which a touch input results in an analog signal which varies in strength in proportion to the touching force or proximity of an object to a sensing element.
Certain improvements may also be made to existing screen designs to provide both programmability of sensitivity and areas of varying sensitivity at the time of manufacture. For example, screens constructed in accordance with either the cited Herbert patent or the Gerpheide, et al. patent may be modified by incorporating a resilient, compressible layer. The compressible nature of the layer will result in an analog screen output signal. Additionally, a resilient, compressible layer having regions of varied thickness may be incorporated in either screen at the time of manufacture to provide different levels of touch sensitivity.